At present, there are two methods to measure optical radiation. One approach is to obtain the photometric and colorimetric quantities by measuring the spectral power distribution of an object to be detected; and, the other approach is to form various characteristic response functions (e.g., CIE tristimulus value matching functions, (hotopic/scotopic/mesopic) spectral luminous efficiency functions of human eyes, etc.) by using photoelectric detectors and characteristic color filters and then obtain the photometric quantity, the tristimulus value and the like of the object to be detected so as to calculate parameters such as color. Compared with the technical solutions in which the spectral power distribution of the object to be detected is accurately measured, a photoelectric detection system using a combination of color filters and photoelectric detectors is apparently more advantageous in terms of the measurement time and cost.
Conventionally, there are following methods to measure an object to be detected by using a combination of photoelectric detectors and color filters.
(1) A large number of narrow-band color filters are successively placed in front of detectors (e.g., silicon photocells, monochrome CCDs, etc.) (taking the visible light at 380 nm to 780 nm as example, in order to realize the resolution of 10 nm, at least 40 narrow-band color filters with a transmitted waveband of 10 nm are required). The detectors receive response values at different narrow-bands and then integrate a plurality of response values, so as to measure a spectral power distribution within a detection waveband and to obtain various photometric and colorimetric quantities according to the spectral power distribution. However, this method is realized by switching between a large number of narrow-band color filters, and is thus high in cost, complicated in apparatus structure, tedious in operation and time-consuming.
(2) Color filters with different spectral response characteristics are placed in front of detectors (e.g., silicon photocells, monochrome CCDs, etc.), and the response function of the detectors and the different color filters constitute different combined spectral response functions to realize the measurement of different photometric and colorimetric quantities. However, by this method, it is unable to obtain the spectral power distribution of the object to be detected, and this method is limited by various factors such as process, environment and cost. Moreover, there is a large difference between the actual spectral response function formed by the detectors and the color filters and the theoretical response function (e.g., the CIE tristimulus spectral response function), resulting in low measurement accuracy. Therefore, this method cannot be applied in high-accuracy measurement fields.
In addition, CN201464052U disclosed a multi-spectra temperature measurement device based on a color CCD, wherein a three-channel color filter with a narrow-band spectral transmittance response characteristic is placed in front of the color CCD, and the three narrow-band spectral transmittance responses have red, green and blue single-peak central wavelengths. During the measurement, light passes through this color filter, so that a plurality of measurement signals with different spectra may be obtained simultaneously. Thus, the measurement of color temperature is realized, and the demand for the measurement of a high-temperature field may be satisfied. However, this method cannot be applied in an occasion where more spectral measurements are needed.
In conclusion, in the prior art, due to the use of a spectrometer of high cost, or due to low measurement accuracy, tedious operation or single test function, the effects of high measurement accuracy, powerful function, simple operation, low cost and the like cannot be all realized.